Propeller



Nov. 8, 1966 J. AUMARECHAL 3, 83,829

PROPELLER Filed Sept. 4, 1964 Jaques Aumarechal INVENTOR ATTORNEY United States Patent 2 Claims. (a. 170-159 This invention relates to propellers of the screw type, and has more particularly for an object to construct these propellers to avoid the harmful effects of cavitation, particularly at high speeds of revolution.

To this effect, I modify the leading edge of the propeller blades by cutting therein serrations or teeth of a particular form. These serrations or saw-teeth prevent the fouling of the propeller by objects floating in the water, seaweed, rope-ends, roots, which tend to tangle in, and paralyze, the propeller, and which may cause shipwrecks.

Since the speed of revolution of the propeller is no longer limited, when the propeller is constructed according to my invention, the latter also contemplates the use of a series of small propellers, revolving at high speed, directly coupled to a steam or gas turbine and so constructed as to be fitted to various points of the hull of a ship.

These and other characteristics of my invention will appear from the appended drawing, which are not to be taken as limiting the scope of my invention and in which:

FIG. 1 shows, in elevation, a portion of a propeller provided with teeth-like serrations on its leading edge. The saw moves in the direction of the arrow.

FIG. 2 shows, in cross-section taken along line X-X of FIG. 1, the serrations or saw-teeth, and the movement of the water streams through said teeth.

FIG. 3 illustrates a type of propeller with curved blades, the leading edges of which are serrated in accordance with my invention.

FIG. 4 illustrates an embodiment of my invention, in which a serrated propeller is connected to and carried by the shaft of a motor, the motor being enclosed in a bulblike container, from which the shaft protrudes, the container being inside of a tube, open at both ends and through a liquid flows; the figure shows a section of said tube, in cross-section.

Referring to FIGURE 1, the shape of the teeth is shown by reference to the numerals 2, 3, 4 and 5. The leading edge of the propeller is numbered 1. The teeth resemble a trapezoid modified by the fact that the angle formed by one side and the outer side, as shown by points 2-3-4, is approximately 90; the side 2-3 is the trailing edge. The angle formed by the outer edge or cutting edge and the forward edge of the teeth, shown at 3-4-5, is about 135.

As an example, in a small propeller, having a diameter net in excess of 300 mm., the length of the outer edge 3-4 may be 10 mm., the length of the leading edge 4-5 may be 6 mm., while the height of the trailing edge may be 4 to mm. between points 2-3 and 5-6.

The outer edge 3-4 is the true cutting edge of the propeller through the water and it is carefully bevelled, as shown at B in FIG. 1. The leading edge 4-5 and the trailing edge 2-3 are also beveled, the bevels being substantially parallel, as shown in FIG. 2 at b and b so as to form, between the front face 7 of the propeller and its rear surface 8, channels 9 through which the water flows during rotation of the propeller, as indicated by the arrows inside said channels in FIG. 2. Between the rear face and the front face of the propeller, the slope of the bevels is from back to front in relation to the direction of motion of the propeller saw-teeth, shown again by the arrow over FIG. 2. This insures an easy passage of the water streams through channels 9.

My design provides for a substantial clearance between successive saw-teeth to obtain a better attack of the propeller in the water, which is considered to be a compressible and semi-elastic medium.

The embodiment illustrated in FIGURE 3 shows my invention applied to a three-blade propeller. The blades 10, 11 and 12 are attached to a central hub 13 with a geometrical pitch of 45. The propeller rotates in the direction of the arrow. The leading edges of the three blades have been machined to provide therein saw-teeth serrations similar to those described and illustrated in FIGURES 1 and 2.

The embodiment illustrated in FIGURE 4 shows a propeller 18 connected to the shaft of a meter enclosed in a fluid-tight bulb 15 located within a tube 14, open at both ends, and a section of which is illustrated, and submerged in water or other fluid. The bulb 15 is held in place in tube 14 by two hollow supports 16 and 17. The motor may be an electric motor or a gas or steam turbine. The inlet and outlet channels for the electric current or for the gas or steam are inside the hollow supports 16 and 17 The propeller 18 is serrated according to the principle of my invention as described herein in connection with FIG- URES 1 and 2. It revolves at high speed, creating a powerful jet, which propels the water or other fluid from left to right as shown by the arrow in FIGURE 4.

A number of units illustrated in and described with respect of FIGURE 4 can be installed at various points of the hull of a ship, and the plurality of jets so produced propels the ship, and may thus replace the traditional propellers installed aft the ship.

It will be understood that the bottom of the supports 16 and 17 are suitably connected with the supply and the exhaust means for the current or the gas or steam, which are usually inside the ship.

The system of propellers according to my invention may also be installed in an oil pipe-line, to circulate continuously the oil, thus replacing presently used high pressure pumping stations; the system here referred-to is that shown in FIGURE 4.

Also, the bulb unit, such as shown in FIGURE 4, being reversible, it can be inserted in a penstock. The propeller 18 works as a turbine, driving a dynamo contained in the bulb 15 to produce electric energy.

I claim:

1. A propeller comprising at least two blades attached to a central hub, in which the outer edge of each blade is serrated with saw-like teeth having a substantially trapezoidal profile including in each serration :an elongated arched outer cutting edge, an inwardly cut leading edge and an inwardly cut trailing edge; in which the angle formed between the trailing edge and the outer cutting edge is about and the angle formed between the outer cutting edge and the leading edge is about in which said trailing edges and said leading edges are bevelled through the thickness of the blades, the surfaces of said bevelled edges being substantially parallel to each other, the slope of the bevelled surfaces being inclined from the rear face to the front face of the blades in the direction of the propellers revolution; in which said angles provide for a substantial clearance between two successive teeth and form an ample channel for the flow of the fluid during rotation of the propeller; in which said outer cutting edge of the teeth is bevelled to reduce the thickness of the teeth at their outer edge and to form a sharp cutting edge.

2. A propeller as claimed in claim 1 comprising three blades attached to a central hub with a geometrical pitch of about 45, the radius of the outer edges of each blade increasing progressively rearwardly with respect to the direction of revolution of the propeller.

References Cited by the Examiner UNITED STATES PATENTS 725,639 4/1903 Webber 170- 159 978,677 12/1910 Taylor 170 159 1,262,422 4/1918 Wood 103111 1,862,827 6/1932 Parsons et al.

4 FOREIGN PATENTS MARTIN P. SCHWADRON, Primary Examiner.

JULIUS E. WEST, SAMUEL LEVINE, Examiners.

E. A. POWELL, JR. Assistant Examiner. 

1. A PROPELLER COMPRISING AT LEAST TWO BLADES ATTACHED TO A CENTRAL HUB, IN WHICH THE OUTER EDGE OF EACH BLADE IS SERRATED WITH SAW-LIKE TEETH HAVING A SUBSTANTIALLY TRAPEZOIDAL PROFILE INCLUDING IN EACH SERRATION AN ELONGATED ARCHED OUTER CUTTING EDGE, AN INWARDLY CUT LEADING EDGE AND AN INWARDLY CUT TRAILING EDGE; IN WHICH THE ANGLE FORMED BETWEEN THE TRAILING EDGE AND THE OUTER CUTTING EDGE IS ABOUT 90* AND THE ANGLE FORMED BETWEEN THE OUTER CUTTING EDGE AND THE LEADING EDGE IS ABOUT 135*; IN WHICH SAID TRAILING EDGES AND SAID LEADING EDGES ARE BEVELLED THROUGH THE THICKNESS OF THE BLADES, THE SURFACES OF SAID BEVELLED EDGES BEING SUBSTANTIALLY PARALLEL TO EACH OTHER, THE SLOPE OF THE BEVELLED SURFACES BEING INCLINED FROM THE 